1. Field
The instant invention relates to electrolytic-type sodium ion sensors which employ a sodium transport electrolyte in conjunction with a pair of electrodes, one of which is exposed to the medium to be analyzed, and the other being a reference electrode. Concentration of the sodium ion is determined by the voltage generated by the difference in ion concentrations between the reference material, which has a known sodium ion concentration, and the medium to be analyzed. The voltage is translated into an ion concentration differential according to the Nernst equation.
2. State of the Art
Ion concentrator analyzers have been utilized in industry for some time. A typical sodium ion analyzer, for example, has a solid sodium ion transport electrolyte in contact with a solution of known concentration and a reference electrode sealed so that an outer surface is exposed to the solution to be analyzed. The other electrode makes contact with the solution to complete the circuit. Since the solid sodium ion transport electrolytes, which are water resistant, such as NASiCON, are influenced by protons, that is the hydrogen ion, the solutions must be buffered to a substantially high pH, typically up to pH&gt;9.0 where H.sup.+ concentration is very low. Also, other alkaline metal and alkaline earth metal ions may influence detected voltage differentials, that is, some of them may be transported to some small degree in the sodium ion transporting electrolyte. The transportability of protons and other alkali and alkaline metal species causes such sodium ion solid electrolyte sensors to give inaccurate indications of sodium ion concentration.
Other sodium ion concentration analyzers employ chemical analysis when very accurate readings are required. The existing solid sodiumion electrolyte analyzers generally do not give the accuracy provided by wet chemical analyzers.